1. Field of the Invention
The present invention relates to a semiconductor device and a method of manufacturing the same, and more particularly to a semiconductor device which contains a plurality of wirings juxtaposed with one another and uses SiOF as an insulating film, a semiconductor device having multilayer metallization and uses SiOF as an interlayer insulating film, and a method of manufacturing these semiconductor devices.
2. Description of the Related Art
Following the enhancement in integration degree and micro-structure design of semiconductor devices, there have been tendencies to reduce the wiring pitch and increase the parasitic capacitance (called as "wiring capacitance") attendant to wirings. Materials having lower specific dielectric constant have been used as interlayer insulating films to reduce the wiring capacitance. Of these materials, SiOF is an insulating material having the lowest specific dielectric constant in inorganic materials formable by a plasma CVD method which has been hitherto used.
A semiconductor device using SiOF as an interlayer insulating film will be described with reference to FIG. 1 and FIGS. 2 to 4.
FIG. 1 is a cross-sectional view showing a conventional semiconductor device, and FIGS. 2 to 4 are cross-sectional views showing a method of manufacturing the semiconductor device shown in FIG. 1. In this case, a three-layer metallization structure is shown. As shown in FIG. 1, an interlayer insulating film 12 formed of SiOF is provided in a wire gap portion of a first layer wiring 8 and at the upper side of the first layer wiring 8, and also an interlayer insulating film 17 formed of SiOF is provided in a wire gap portion of a second layer wiring 15 and at the upper side of the second layer wiring 15. The thickness of the interlayer insulating film 17 is set to 0.6 micrometer to 1.0 micrometer at the upper side of the second layer wiring 15.
A method of manufacturing such a conventional semiconductor device will be described with reference to FIGS. 2 to 4.
First, as shown in FIG. 2, a diffusion layer 1 and the element isolation region 2 are formed on the semiconductor substrate 3, and the first interlayer insulating film 4 is grown on the diffusion layer 1 and the element isolation region 2. Then a barrier metal layer 5A, an aluminum layer 6A and a titanium nitride layer 7A are successively formed. Thereafter, a desired pattern is left to form the first layer wiring 8, and SiOF film 11 is formed thereon.
Subsequently, as shown in FIG. 3, SiOF film 11 is flattened to form a flattened SiOF film 9. Then, as shown in FIG. 4, a viahole 13 is selectively formed in the SiOF film 9 on the first layer wiring 8 to form a second interlayer insulating film 12, a tungsten plug 14 is formed in the viahole 13, and a barrier metal layer 5B, an aluminum layer 6B and a titanium nitride layer 7B are successively formed. Thereafter, a desired pattern is left to form the second layer wiring 15.
Subsequently, as shown in FIG. 1, a third interlayer insulating film 17 having a viahole 18 is formed, a tungsten plug 19 is informed in the viahole 18, and a barrier metal layer 5C, an aluminum layer 6C and a titanium nitride layer 7C are successively formed. Thereafter, a desired pattern is left to form the third layer wiring 20. Then, a cover film 21 is formed, thereby completing the final structure shown in FIG. 1.
In the semiconductor device thus constructed, when the fluorine concentration in SiOF constituting the interlayer insulating film is set to be less than 5 atom %, any effect of reducing the dielectric constant cannot be obtained. Therefore, the wiring capacitance is increased, resulting in reduction of a circuit operating speed and increase of power consumption. On the other hand, if the fluorine concentration in SiOF constituting the interlayer insulating film is set to 5 atom % or more, exfoliation of the interlayer insulating film or the wirings is more liable to occur, and the yield is reduced. That is, for the conventional semiconductor device, it has been difficult to set the optimum fluorine concentration.